JPS6285525A - Control method for transmission right - Google Patents

Abstract

PURPOSE:To reduce the probability of mutual interference among stations by checking the presence or absence of an idle channel from the time of observation varied by the channel priority and using the idle channel. CONSTITUTION:The channel number of the highest priority is read out of a memory 17 when a transmitting request is received and a synthesizer 18 is set at a frequency accordant with said channel. Then the reception signal is converted into an intermediate frequency by the output of the synthesizer 18 and undergoes the wave detection through an wave detector 12. While the reciprocal number of a priority function is read out of the memory 17 and set to a counter 16. An integration circuit 13 integrates the output of the detector 12 for the time set to the counter 16 and delivers it to a deciding circuit 14. The circuit 14 decides an idle state of the circuit by the output of the circuit 13. Thus the integration is applied for a long time to the channel having the small priority function and an idle circuit is accurately decided. While the integrating time is reduced to the channel of the large priority function and therefore the waiting time is reduced. This reduces the probability of mutual interference among stations.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a communication system in which multiple stations share multiple channels, such as a local area network (LAN).
and transmission right control methods for wireless communication systems.

(Prior art and its problems) Traditionally, systems in which multiple stations share and use multiple channels include wireless communication systems such as satellite communication and mobile communication, and LAN, especially data communication called broadband LAN. There is a network. In a mobile communication system, for example, in an automatic JJLt communication system, a central station manages all channels, and when a mobile terminal requests to use a line, the central station specifies an empty channel, and the slave station transmits on that channel. The method is to obtain rights. If there is only one central station, this method does not cause any problems, but if there are multiple central stations, multiple central stations may use the same frequency channel at the same time, causing interference. To prevent this, measure the propagation distance of radio waves, set a communication zone for each central station, specify that adjacent communication zones use different frequency channels, and reuse the same frequency. A method is used to create a zone that is sufficiently far away so that no interference occurs. Details of the design method of such a system can be found in the literature (Ito, Matsuzaka, [Overview of car telephone system], Research and Practical Application Report, Vol. 26, No. 7).
No. 1821-1836, 1977).

However, in such a cell system, frequencies cannot be used sufficiently effectively. In other words, since it is decided that adjacent zones use different frequencies, there will be fluctuations in the amount of traffic, even if the amount of traffic in a particular zone is very high and the amount of traffic in the surrounding zones is small. Since frequency channels in adjacent zones cannot be used, call loss occurs in zones with high traffic volume, and zones with low traffic volume are hardly used. A possible solution to this problem is to observe all frequency channels at each central station and use the available channels. However, with this method, even if the central station observes that the channel is free, the mobile terminal may experience interference, so it is not possible to determine the frequency channel to be used only by the central station. Therefore, there is a drawback that several exchanges are required between the central station and the mobile terminal before determining the frequency channel, which takes time.

Furthermore, in mobile communications, there is a fluctuation in the received electric field called fading, so it is difficult to correctly detect the presence of interference waves, and there is also a disadvantage that there is a fairly high probability that interference waves will be missed.

Similar technical problems also exist in local area networks (LANs), which are systems completely different from mobile communication systems. Various methods have been proposed for controlling transmission rights to lines in LANs, and one of the most popular methods is a multi-channel type C8MAy'CD method. This method is described in the literature (Nomura, Okada, Nakanishi ``
Multichannel C8MA/CD system in broadband path network - Sato-netJ + IEICE Technical Report 5
E83-291983). In this system, multiple terminals are coupled via a common bus, and multiple frequency channels can be used on the bus. A terminal that has data to send finds an available line and sends it. In a LAN, unlike in the case of mobile communications, there are almost no cases where a signal cannot be detected even though it is being transmitted, but if two terminals start transmitting on the same channel almost at the same time, due to propagation delay, Sometimes a terminal starts transmitting without realizing that the other terminal is transmitting, causing a collision. The probability of such a collision sets the upper limit of the effectiveness of line usage, and there is a drawback that the line usage efficiency cannot be improved if the propagation delay becomes large.

One way to solve this problem is to assign priorities to channels for each system or terminal, and use channels in order of priority in each system. If the priorities are arranged in different orders between systems, the probability of interference is greatly reduced. The method for determining this priority order is the patent application filed on June 5, 1985.
It is described in detail in the specification of No. 2223 [Transmission right control method] (Reference 1).

In this way, if each system uses different channels in order, the probability of interference will be greatly reduced, but the overall amount of traffic will increase, and the situation where all channels are being used will increase. After all, there is a high probability that interference will occur.

(Objective of the Invention) The purpose of the present invention is to eliminate the drawbacks of the conventional transmission right control method described above, and to provide an efficient transmission right control method that has a low probability of causing interference even when the amount of traffic is large. be.

(Invention of the Invention) According to the present invention, in a communication system in which a plurality of stations share a plurality of channels, each station assigns priorities among channels based on one past history, and To provide a transmission channel control method in which, when channels are used in ascending order, the channel is observed over a period of time determined by priority prior to channel use, and transmission is performed after confirming that the channel is free. I can do it.

(Principle of the Invention) The system and problems to be solved by the present invention can be abstracted and described as follows. Although a plurality of stations use a plurality of channels, each station independently determines the channel to be used without any particular exchange of information. In this case, if multiple stations try to use the same channel at the same time, they will interfere with each other and neither will be able to properly transmit information. Therefore, it is necessary to ensure that each station uses different channels as much as possible to avoid interference. One possible means for this is to observe the channel prior to transmission and confirm that the channel is empty. However, due to the incompleteness of observation, there is still a possibility that free channels cannot be correctly identified and interference will occur. Therefore, in the present invention, the channels used for each station are prioritized, and the highest priority
We will use them one by one starting from one station. If different channels are given higher priority for each station, the probability of interference will be greatly reduced.

Even if different channels are set to have higher priorities in each station, the probability of interference will still increase as the overall traffic volume increases. In the case of voice communication, this phenomenon leads to quality deterioration, and in the case of data communication, it causes a shank and causes the entire network to malfunction. In order to avoid such a situation, flow control for controlling the amount of traffic can also be determined based on past usage results. In other words, flow control can be realized by restricting the use of channels that have a low priority and have often been used by other stations in the past even if there is a request for use.

However, if such flow control is not performed properly, the overall efficiency will decrease. The simplest flow control method is to control each system so that it does not transmit to channels below a certain priority level, but this method causes traffic to fluctuate temporarily and cannot cope with the situation where one system occupies all the traffic. Therefore, the present invention adopts a method of reducing interference by changing the channel observation time according to the priority order.

In general, in wireless channels, there are fluctuations in the received electric field level due to fading, and a major cause of interference is that a channel may be determined to be an empty channel even though it is actually used by another system. The probability of such observation errors can be reduced by lengthening the observation time. Since there is a small probability that a channel with a high priority is being used by another system, it may be determined that it is an idle channel within a short observation time. In the case of data transmission over a LAN, the priority of a terminal with a long observation time is relatively lowered, so that the probability of collision can be reduced.

(Example) The present invention will be explained in detail below using the drawings.

FIG. 2 is a diagram showing the concept of a system when the present invention is applied to a mobile communication system.

In FIG. 2, sl, s2. s3 are respectively central stations T1
．． T2゜T3. T4. T5. T(3 indicates each mobile terminal, and it is assumed that they communicate with the central station with the strongest received electric field.

In FIG. 2, sl, s2. It is assumed that the communication zones of s3 completely overlap and that simultaneous use of the same frequency channel will cause interference. However, it may fail to detect whether the channel is empty.

Each channel has a priority function P(i
), (i is the channel number). Figure 3 (a), (b), (c) shows how this P(i) changes.
Shown below. The initial value is sl as shown in Figure 3(a).
, s2. It is assumed that P(i) is equal for all stations in s3. Assume that a usage request has now arrived at S1. Sl monitors channel #1, confirms that it is empty, and transmits a paging signal to channel #1. At this time, since the signal was transmitted to channel #1 in Sl, P(1) is increased. followed by S
Assume that a usage request occurs in step 2. In S2, channel #1 is first observed, but since it is in use, channel #2 is next monitored. Since it is empty here, 82
uses channel #2. Therefore, in 82, P(
1) is decreased and P(2) is increased. Continue to S3
If a request for use occurs in S3, channel #1
．． Since channel #2 is in use, channel #3 is used. f
In S3, P(1) and P(2) are reduced to P(3).
increase. The state of the priority function in each station at this time is shown in FIG. 3(b). Once there is a difference in priority between channels, each station will preferentially use the channel with the highest priority, so the priority function of the channel with the highest priority will increase rapidly, as shown in Figure 3 (C). It is expected that this will happen.

In this case, Sl will preferentially use channel #1, 82 will preferentially use channel #2, and 83 will preferentially use channel #3, thereby reducing the probability of mutual interference.

However, since each station has a plurality of communicating terminals, the number of channels used is not necessarily one. If another transmission request occurs while 82 is using channel #2, it will monitor channel #1, which has the second priority, and if it is free, channel #2 will be used.
It will be sent to 1. However, as shown in Figure 3(c), the fact that the value of the priority function P(1) for channel #1 is extremely small means that channel #1 is used frequently, and the probability that the observation is incorrect is high. expensive. If you start transmitting in such a case, it may cause interference to other stations in use.
There is a high probability that it will be -. Therefore, when transmitting to a channel where the value of the 1 priority function is small, the probability of interference can be reduced by lengthening the observation time and reducing the probability of observation errors.

FIG. 1 shows a specific embodiment of the transmission right control method according to the present invention. When a transmission request arrives, it is first necessary to observe the channel with the highest priority.

Memory 17 stores information for setting priority function P(i) and channel i in synthesizer 18. When a transmission request arrives, first the number of the channel with the highest priority is read out from the memory 17, and the number of the channel with the highest priority is read out from the memory 17.
is set to a frequency that matches that channel. The output of the synthesizer 18 is multiplied by the received signal in a multiplier 10 to convert the received signal into an intermediate frequency signal. After the intermediate frequency signal is band-limited by a band pass filter 11, it is passed to a detector 12.
The wave is detected by At the same time, from the memory 17, the priority function P
The reciprocal of (i) is read out and set in the counter 16. The value of the counter 16 becomes the integration time of the integration circuit 13.

The integrating circuit 13 integrates the output of the detector 12 for the time set in the counter 16, outputs it to the determination circuit 14, and then resets the integrated value. The determination circuit 14 determines whether the line is free or not based on whether the output of the integrating circuit is a constant value.

In this way, for channels with a small value of the priority function P(i), a long time integration is performed, so it is possible to determine whether the line is free or not more reliably. As for the channel, since the integration time is short, the waiting time can be reduced.

Furthermore, the transmission right control circuit needs to determine the channel to be used. This determination is made by the decision analysis circuit 15.

The judgment circuit makes a judgment based on the following criteria.

(1) If the determination circuit 14 determines that the line is empty, it is determined that the channel should be used, and the information is output from the terminal 101 to the transmission circuit. The frequencies to be used simultaneously are output from terminal 102.

(2) If the determination circuit 14 determines that the line is in use, the next priority channel is observed. However, if all channels have been observed, busy information is output from the terminal 101 to the transmitting circuit.

The contents of the memory 17 can be adaptively changed by the output of the determination circuit. Such an operation is described in the above-mentioned document 1.

Increasing the observation time for channels with low priority can also be effective when applied to the multi-channel C8MA/CD method described above.

In C8MA/CD, especially when a certain channel is occupied by a long message, after the message ends, packets that have been waiting until then are transmitted simultaneously from multiple terminals, often causing collisions. Such collisions can be avoided by observing the line at different observation times for each terminal.

(Effects of the Invention) As described in detail above, the present invention realizes a transmission right control method that can extremely reduce the probability that stations will interfere with each other in a communication system in which multiple stations share multiple channels. can do.

In the embodiment, the channel has been described as a frequency channel in a frequency division system, but the present invention can be applied even if it is considered as a time slot in a time division system.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of an embodiment of the present invention, Fig. 2 is a diagram showing a system in which the embodiment of Fig. 1 is used, and Fig. 3 (
Figures a), (b), and (c) are diagrams showing how the priority changes. In the figures reference numbers 10, 11, 12, 13, 14, 1
5, 16, 17, and 18 indicate a multiplier, a band pass filter, an integrating circuit, a determining circuit, a determining circuit, a counter, a memory, and a synthesizer, respectively. Kaya 7T! 1

Claims (1)

[Claims] A transmission right control method in a communication system in which a plurality of stations share a plurality of channels, in which each station gives priorities among the channels based on past history, and uses the channels in the order of the highest priority, the method comprising: Observe whether the channel is an empty channel before using the channel,
A transmission right control method characterized in that transmission is performed when a channel is determined to be empty, and the observation time is varied depending on the priority order of each channel.